The present invention relates to an optical monitoring device for monitoring the activity of a tool in a monitoring region, having at least one camera.
Such a monitoring device is suitable for many types of tools and is not limited to any one particular type of tool; therefore, the tool may be, for example, a welding, riveting, or soldering device, a device for applying adhesive, for example, in the form of an adhesive bead, to a workpiece to be adhered, a common sensor element, for example, for scanning surfaces, or any sort of implement or application tool, the activity of which must be monitored. Other areas of application for such a monitoring device are inspection, for example, in the context of quality control and/or the processing of objects such as an adhesive bead, a seam, a joint, and edge, and/or a surface. An optical monitoring device according to the invention is particularly suitable for robotically operated tools whose function must be monitored.
The monitoring device monitors the activity of such a tool in a monitoring area that may include, for example, the immediate working area of the tool. The term “working area of the tool” is to be understood in this context as the three-dimensional area in which the tool operates. Moreover, the monitoring area may also comprise an optionally three-dimensional area that is not the working area of the tool but preferably is associated with the activity of the tool, for example, an area adjacent to the working area that is used for quality control of the object processed in the working area.
An optical monitoring device for monitoring a working area and/or monitoring area having at least one camera is disclosed in DE 203 07 305 U1. The known monitoring device may be fixed to the tool such that the visual range of the camera is always directed at the monitoring area, even if the tool and/or an object to be processed moves. In a preferred embodiment, the optical monitoring device is embodied such that the visual ranges of at least two, preferably three, cameras overlap in the monitoring area.
EP 1 697 061 B1 and EP 1 701 801 B1 disclose a similar device for detecting a structure to be placed on a substrate, preferably an adhesive bead or adhesive track. The sensor unit of such a device comprises a plurality of cameras, with the cameras each being directed towards the unit for applying the structure and being disposed around said unit.
However, the methods mentioned above have the disadvantage that the field of view of a camera cannot be used sufficiently in measuring a three-dimensional object (for example, an adhesive bead), particularly with regard to analyzing the sides of the object. For such an analysis, the object to be examined requires an image of the object from a 360° periphery, which requires the use of multiple cameras when using the conventional methods.
An additional disadvantage to the use of the known methods lies in the fact that the visual lines of the camera diverge during optical imaging by means of a camera, particularly when short focal distances are used. This is due to the fact that the optical image of a camera is fundamentally a central projection. This is a disadvantage when, for example, an adhesive or sealing bead is viewed from the top and said view is used to draw conclusions regarding properties of the object from the side because, depending on the angle of view, it is typical for one edge to be poorly visible or not visible at all.